Dielectric honeycomb core materials see a variety of uses in microwave applications. Such honeycomb materials are used to provide loading within waveguides and to provide structural supports for high frequency components. In certain applications, it is required that the permittivity of the honeycomb material be known precisely. Since permittivity values of honeycomb core can vary over a substantial range, it is desirable to test the permittivity of the core structure prior to its actual use. In such a test, the permittivity is measured of different sections of a large core block, before the block is machined and parts installed. Clearly, any testing of the honeycomb core should be non-destructive, be accomplished rapidly, and provide accurate results.
The prior art illustrates a variety of applications of dielectric core structures and their application to waveguide systems, but does not indicate a method for rapid non-destructive testing of honeycomb material. U.S. Pat. No. 2,840,788 to Mullett, et al discloses the use of various shaped dielectric structures to provide internal waveguide loads. U.S. Pat. Nos. 3,234,489 and 3,337,822, both to Hahne, describe various applications of cellular supporting dielectric structures that are used to provide physical support for metallic waveguides. U.S. Pat. No. 3,771,077 to Tischer describes the use of metal posts that are mounted on a dielectric surface to provide a segmented waveguide structure. U.S. Pat. 3,474,354 to Simon discloses the use of transverse metal rods as loads in a waveguide structure. The rods are mounted transversely to the direction of wave propagation and thereby provide a loading effect within the waveguide. U.S. Pat. No. 3,560,695 to Williams, et al. also discloses the use of conductive rods for reactively loading a flat waveguide structure. U.S. Pat. 3,944,326 to Tacke, et al. discloses the use of a segmented grating as a waveguide structure.
U.S. Pat. No. 2,464,269 to Smith discloses the use of dielectric posts for polarization control in a waveguide. U.S. Pat. Nos. 3,801,939 to Lamy, et al. and 4,862,186 to Strider both disclose segmented waveguide structures wherein subcomponents mount together to provide an overall waveguide arrangement.
As above indicated, waveguides with dielectric inserts are found in a number of applications. For example, multi-layer dielectric structures are used in phased array antenna systems to form the aperture assembly for each phase control module mounted in the antenna face. Such structures require an RF conduit embedded in the dielectric structure. U.S. Pat. No. 4,918,411 to Staeblin et al. shows such a structure with a grid-like waveguide assembly embedded in laminarly-assembled dielectric layers. The grid-like structure defines a waveguide and provides an RF signal transmission path through the layers of dielectric material positioned within the interior of the grid-like structure. The grid-like structure is not readily removable from the dielectric as it is embedded and integral therewith.
Accordingly, it is an object of this invention to provide a demountable waveguide structure particularly adapted to rendering of permittivity tests on a honeycomb dielectric.
It is another object of this invention to provide a demountable waveguide structure that may be rapidly assembled and disassembled and provides a non-destructive arrangement for making permittivity tests of a dielectric media.